1. Field of the Invention
The present invention relates to a developer processing apparatus for supplying or stirring a developer. More specifically, the present invention relates to a developer processing apparatus having a sealing member and a sealing layer provided at a portion rotatably supporting a member for supplying or stirring the developer.
2. Description of the Background Art
In an image forming apparatus employing electrophotography such as a copying machine or a printer, a developing apparatus is provided for forming a latent electrostatic image on a surface of a photoreceptor as a recording medium, supplying a developer such as toner for measuring the latent image to the surface of the photoreceptor and for applying the developer on the image.
In the developing apparatus, the latent electrostatic image formed on the surface of the photoreceptor is developed, and the developed toner image is transferred onto a transfer material such as a sheet of paper. After the toner image is transferred, part of the toner which has not fully been transferred is left on the surface of the photoreceptor. The residual unnecessary toner is removed from the surface of the photoreceptor so as to form next image repeatedly. Therefore, a cleaning apparatus for removing the toner left on the surface of the photoreceptor after transfer is provided, and the unnecessary toner removed by the cleaning apparatus is put in a container unit in the cleaning apparatus.
As described above, conventionally, a developing apparatus for developing the latent electrostatic image formed on the surface of the photoreceptor and a cleaning apparatus for removing the toner left on the surface of the photoreceptor have been provided, and by these apparatuses, the toner in the form of fine particles must be processed. In order to process the toner as a developer, a rotary member is provided in a container forming part of the developing apparatus or the cleaning apparatus, that is, a developer tank in the developing apparatus and a toner container unit in the cleaning apparatus, for supplying and processing the toner.
The rotary member provided for the developing apparatus includes a stirring member for stirring the developer in the developer tank, and a supply member for supplying the developer to the photoreceptor. A rotary member which is rotary driven for supplying and stirring the developer is also provided at a member for supplying toner to the developer tank. These members constitute the developer processing apparatus.
Further, in the cleaning apparatus, a supply member for feeding toner contained temporarily in the container unit to the recovery container, for example a screw member, is provided as a rotary member. Rotary member and the toner container unit are components of the developer processing apparatus.
The aforementioned rotary members are rotatably supported at the toner container unit of the cleaning apparatus or at the developer tank constituting the developing apparatus. Therefore, it is possible that fine powder of toner enters the supporting portion supporting the rotary member, causing failure in rotation.
Japanese Patent Laying-Open No. 3-189666 discloses a conventional technique for supporting the rotary member. In this technique, a sealing member (such as a V ring) formed of rubber, for example, is provided for sealing the portion supporting the shaft of the rotary member, so as to prevent entrance of powder, such as toner, to the supporting portion.
Japanese Utility Model Laying-Open No. 3-20356 proposes a technique in which a sealing member formed of stainless steel, for example, is provided at the portion supporting the shaft of the rotary member, and an edge (bellows) of a V ring having a V shaped groove is brought into pressure contact with the sealing member for tight sealing, whereby entrance of the fine powder such as toner to the bearing portion is prevented.
According to the prior art described above, in a developing apparatus including a toner supply unit or in a developer processing apparatus provided at the cleaning apparatus, the rotary member for stirring or supplying the developer is rotatably supported by a supporting unit provided in a container containing the developer, and entrance of the developer at the supporting portion is effectively prevented. Accordingly, failure in rotation caused by the entrance of the developer is prevented.
However, generally, resin material, which is easy to mold and inexpensive is generally used for the developer tank and the container unit of the cleaning apparatus for supporting the rotary member as well as a screw roller, for example, serving as the rotary member for supplying or stirring the developer. Metal material such as aluminum or stainless steel is commonly used for the shaft for rotating the screw roller and the support portion, in view of strength and durability.
The screw roller as a resin molded rotary member mentioned above is charged by friction while it supplies the developer, and by the charges, a potential of several hundreds to several thousands volts is generated at the surface of the resin member. This causes an electric field between the resin member and the shaft or supporting member rotatably supporting the rotary member, so that charge developer adheres and coagulates on the shaft and supporting member. Therefore, even when the above described member for preventing entrance of the prior art is provided, the developer unavoidably enters the support portion after long time of operation, possibly causing failure in rotation.
Referring to FIGS. 1A and 1B, for example, when rotary member 5 rotates, the container 3 itself or a vane 5a of the rotary member 5 is charged positive by friction with the developer contained in the container 3. Charges of opposite polarity comparable to the charges are induced on a conductive rotary shaft 50, whereby an electric line of force runs therebetween, generating an electric field. The toner, which is the developer 2 charged along the electric field, especially along the electric line of force adheres on the rotary shaft 50 and is coagulated gradually. Therefore, even when sealing member (V ring) 53 is provided, developer 2 gradually enters the bearing unit 52.